1. Field of the Invention
The present invention relates to components for breathing circuits and in particular to conduits for use in the limbs of breathing circuits. The invention also relates to methods of manufacturing such conduits.
2. Summary of the Prior Art
In assisted breathing, particularly in medical applications, gases are supplied and returned through conduits. Such conduits are ideally light and flexible to ensure the greatest level of comfort for the patient. In the prior art, thin walled conduits are known which include helical or annular reinforcing ribs which act to give the conduit better resistance to crushing and pinching, while still allowing the conduit to be light and flexible. An example of one such conduit is shown in FIG. 1.
It is advantageous to manufacture this type of conduit as a continuous process. In the prior art this is achieved by spiral winding of a thin polymer tape onto a former such that the edges of adjacent layers overlap a small amount. A bead of molten polymer is then applied over the top of the overlapping edges welding them together and simultaneously forming the helical reinforcing ribs. To form a heated conduit, one or more heater wires are positioned on the polymer tape or film as the tape is drawn onto the former. The wires must be accurately positioned adjacent the free edge of the tape, to be covered by a subsequent turn and then by the molten bead. Continuous accurate positioning can be difficult to achieve, and if it is lost the wire can be exposed to either the inside or outside of the tube instead of being encapsulated in the conduit wall.